Conventional burning bars which are used on land for cutting structural materials such as rock, stone, concrete, iron and steel are disclosed in any of U.S. Pat. Nos. 3,260,076; 3,507,231; 3,487,791; 3,500,774; 3,507,230; 3,570,419; and 3,738,288. The burning bars shown in the foregoing patents share a common feature in that they have an outer tube within which is placed a plurality of elongated rods or wires to make up a mass of oxidizable metal. Oxygen is conducted down through the outer tube to the end of the rod where combustion is initiated to produce a flame which is directed at the structural material. The preferred burning bars usually contain a readily oxidizable metal (e.g. magnesium or aluminum) as one or more of the rods to promote combustion.
The use of multiple strands in various configurations for arc welding electrodes is shown in U.S. Pat. Nos. 1,773,653; 2,345,758; 2,806,128 and 3,147,362 it being well known that welding electrodes are generally unsuitable for cutting operations.
It has been known for a long time to form a welding electrode from a strip of metal by a roll forming operation. The welding electrode generally contains a flux or a core material to facilitate the welding operation. U.S. Pat. Nos. 2,565,477; 2,785,285; 3,036,205; 3,457,388; 3,491,225; 3,531,620; 3,542,398; and 3,866,015 disclose and claim such electrodes. A flux cored electrode is a continuous electrode in the form of wire coils used for weld metal deposition rather than cutting. Flux cored electrodes (wire) require continuous application of welding (electric) current through the wire in order to perform a welding operation. Conventional burning bars can sustain combustion on their own without an electrical current. In all of the flux cored electrodes, a non-compressable flux powder supports the outer metal shell during the forming operation. Without the presence of incompressible material, the electrode would entirely collapse upon itself during the forming operation and not maintain its general circular cross-section. Again, it is well known that a flux cored electrode cannot be used in a cutting operation, especially an exothermic cutting operation which requires presence of an oxidizing material. The purpose of the flux is to generally prevent oxidation of the base metal during the welding operation.
Twisted wire or cable-type burning bars or thermal lances are shown in U.S. Pat. Nos. 3,591,758 and 3,602,620.
Multiple wire burning bars have been adapted to underwater use and also can be used on dry land. These are shown in U.S. Pat. Nos. 4,069,407; 4,182,947; 4,416,444; 4,391,209; and 4,437,649.
U.S. Pat. No. 4,114,863 discloses an exothermic (electrode) cutting rod featuring a tube within a tube and wires inside the inner tube.
Lastly, a three nested tube configuration for use as an exothermic electrode is sold by the Arcair Company of Lancaster, Ohio under the trademark SLICE.